To make tagging easier, you can switch to Assign Tags mode.
Right-click one of the tag categories and click Switch to ‘Assign Tags’ mode.

Switching to the "Assign Tags" mode

The Assign Tags Mode

The Tags panel now looks like the figure on the left.

On the right, instead of the circles, you will see square checkboxes.

This relieves you of having to drag items onto the tags. Instead, you can select them in the browser and assign them to the tags simply by clicking the respective checkboxes.
Tags assigned in this way will be displayed with a checkmark.